Laboratory testing of the Ingot WFS

Abstract

The ingot WFS is a new kind of wavefront sensor specifically designed to deal with the elongation of LGS reference sources on ELT-class telescopes. Like the pyramid, it belongs to the family of pupil plane wavefront sensors and can be considered as a generalization of the pyramid WFS for extended, three-dimensional elongated sources. The current design uses a simple, reflective roof-shaped prism to split the light into three pupils that are used to retrieve the wavefront shape. A test-bench has been realized at the INAF-Padova laboratories to test the alignment and functioning of the ingot. The bench is equipped with a deformable lens, conjugated to the pupil plane, able to apply low-order aberrations and with a hexapod for the precise alignment of the ingot prism. In this work we present a robust and fully automated Python-code alignment procedure, which is able, by using the optical feedback from the I-WFS, to adjust its 6-degrees of freedom. Moreover, we report on the tests conducted with the deformable lens to characterize the ingot WFS response to low-order aberrations in terms of sensitivity and linearity. The results are used as a comparison for simulations to validate the ray-tracing modeling approach with the future goal of optimizing the procedure adopted for signal calculation and phase retrieval.

Ingot-like class of wavefront sensors for laser guide stars

“…Furthermore, the three-pupil ingot has been subjected to laboratory testing (Di Filippo et al 2021), in order to analyze experimentally its sensitivity (Radhakrishnan Santhakumari et al 2020), by using a simulated LGS whose brightness distribution along the line of propagation can be properly adjusted to mimic the actual measurements (Gomes Machado et al 2023). Loworder quasi-static aberrations measurable by such a WFS have been used to implement a tool to automatically align the ingot to the 3D images of the LGS as collected by a simulated telescope in a real hands-on optical bench (Di Filippo et al 2022). Actual closed-loop experimental simulations on an optical bench have also been carried out with a simplified model of the ingot (Arcidiacono et al 2020).…”